230  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
at  present  coming  so  largely  from  high-grade  ores  and  is  likely  to 
come  predominantly  from  such  ores  while  they  last.  With  this  state 
of  affairs  it  is  not  surprising  that  efforts  of  iron  and  steel  companies  to 
secure  the  iron  ore  necessary  for  their  future  existence  should  have 
been  strenuous  in  recent  years,  and  that  deposits  previously  considered 
to  be  too  remote  or  of  too  low  grade  to  be  of  value  should  be  caref ulty 
investigated  for  future  availability  and  remote  areas  explored  for  the 
discovery  of  new  deposits.  Among  the  remote  deposits  long  known 
the  southern  Utah  deposits  are  receiving  much  attention. 
The  following  discussion  is  based  on  a  brief  examination  of  the 
southern  Utah  deposits  by  the  writer  in  the  fall  of  1903.  The  writer 
was  accompanied  by  Mr.  Oscar  Rohn,  a  mining  engineer  from  the 
Lake  Superior  region,  and  many  of  the  points  here  discussed  were 
noted  jointly  with  him.  No  detailed  examination  or  mapping  was 
attempted. 
Distribution  and  geologic  relation  of  the  ores. — The  deposits  are 
located  along  the  slopes  of  a  spur  of  the  Wasatch  Mountains  border- 
ing the  west  side  of  the  High  Plateaus  of  Utah,  where  the  mountains 
break  off  to  the  Escalante  Desert  to  the  west.  The  area  is  represented 
on  a  topographic  map  of  the  Powell  survey,  published  in  Button's 
"High  Plateau"  Atlas,  Iry  a  map  Iry  Putnam  in  the  Tenth  Census 
report,  based  on  the  Powell  Survey,  and  by  the  St.  George  topo- 
graphic sheet  of  the  United  States  Geological  Survey,  also  based  on 
the  Powell  Survey.  The  district  is  reached  by  taking  the  Salt  Lake, 
San  Pedro  and  Los  Angeles  Railway  to  Lund,  and  thence  by  stage 
about  22  miles  across  the  Escalante  Desert  to  Iron  Springs  and  Iron 
City,  adjacent  to  which  the  ores  are  located. 
Sediments  not  markedly  inclined  from  the  horizontal,  described  as 
Lower  Silurian  by  Newberry,  are  intruded  by  andesite.  The  andesite 
now  forms  cores  of  the  foothills  lying  between  the  elevated  areas  of 
flat-lying  sediments  of  the  Wasatch  to  the  east  and  the  desert  to  the 
west.  The  intermediate  valleys  are  underlain  by  limestone  and  sand- 
stone, but  the  rock  in  immediate  contact  with  the  andesite  on  the  flanks 
of  the  hills  is  for  the  most  part  a  pure,  dense,  gray  limestone. 
The  andesite  has  porphyritic  plagioclase  feldspars  and  augite  in  a 
fine-grained  but  holocrystalline  groundmass  of  which  feldspar,  much 
kaolinized,  is  the  conspicuous  constituent.  The  rock  is  much  weath- 
ered to  a  reddish  color,  and  its  debris  covers  the  slopes,  for  the  most 
part  effectively  hiding  the  more  easily  eroded  limestone. 
Along  and  adjacent  to  the  contact  of  the  andesite  and  limestone  are 
the  exposures  of  the  iron  ores.  These  are  in  several  isolated  groups 
in  a  general  southwest-northeast-trending  area  about  18  miles  long 
and  ranging  from  a  few  feet  to  2J  miles  in  width.  The  ores  appear 
in  conspicuous  narrow  ridges  and  crags,  following  roughly  the  con- 
